On the Nature of Jets Issuing From a Row of Holes Into a Low Reynolds Number Mainstream Flow

Abstract

Measurements are reported of the temperature and velocity fields above an adiabatic flat plate through which air is injected via a row of circular injection holes inclined at an angle of 35 deg to the surface. A mainstream flow of air over the plate is present, with Reynolds number based on stream velocity and injection tube diameter of 3.4 × 103 throughout the experiments. The boundary layer approaching the row of holes is either laminar or turbulent and either fully developed laminar or turbulent pipe flow is present in the injection hole (in the absence of the mainstream). The jets emanate from the holes at a mass flux rate from 0.2 to 2.0 times that of the mainstream flow. Key findings are: (i) a laminar jet can penetrate into the main flow with a smaller mass flux than a turbulent jet; and (ii) a turbulent-approaching boundary layer generates a wider domain of interaction between the jets and the mainstream than a laminar-approaching boundary layer for the same blowing rate.